In this lesson, you will learn how to orchestrate a unified, global lockout strategy across your Linux infrastructure to neutralize compromised credentials during an active security incident.
The Challenge of Distributed Lockouts
When a threat actor attempts to brute-force or credential-stuff your global fleet, relying on local pam_tally2 or pam_faillock configurations on individual servers is insufficient. If a user is locked out on Server A but remains active on Server B, the attacker simply shifts their target. Implementing a global policy requires moving the lockout state out of the local PAM module and into a centralized, resilient source of truth.
Centralizing the Lockout State
Instead of local files, you should integrate your PAM stack with a centralized identity provider (such as an LDAP/Active Directory backend or a distributed Key-Value store). By configuring pam_ldap or pam_sss (System Security Services Daemon), you force the host to query the central authority for the account's "locked" status before granting access.
To implement this, you modify your /etc/pam.d/common-auth to prioritize the network-based authentication module:
# Example snippet for centralized auth
auth [success=1 default=ignore] pam_sss.so
auth requisite pam_deny.so
auth required pam_permit.so
When an incident response team identifies a compromised user, they update the user's status in the central directory. Because every host in your infrastructure is configured to verify this status via pam_sss before permitting a login, the lockout becomes global and near-instantaneous.
Coordinating During Active Threats
During an active threat, you should leverage your existing Ansible automation (from Lesson 902) to verify that all nodes are correctly pointing to the central authentication source. If you detect a massive spike in unauthorized login attempts, your automated response script should trigger a global lockout command on the central directory server, effectively "severing" the attacker's access to the entire fleet simultaneously, regardless of where they attempt to pivot.
Key Takeaway: Global lockouts rely on moving the authentication state from local PAM configuration files to a centralized identity provider, ensuring that an account blocked in the core directory is instantly denied access across the entire infrastructure.